Heat control system



ct.` 13, 1942. T P. c. SMITH 2,293,847 v HEAT CONTROL SYSTEM Filed Jan. s1, 1940 i 'G. n

212 B465 TEMPL'HHV'z/HL' 6.5 "l Emma/voz 4 more economically than heretofore.. y It is known to control the heat supplied to a building or other structure in response to the Patented Och-13, 1942- HEAT coN'rnoL SYSTEM Perry C. Smith, Breton Woods, N.'J.. assignor to -Radio Corporation of of Delaware America, a corporation Application Janary 31, 1940, Serial No.:` 316,629

2 Claims.

This invention relates to he'at control systems, such as respond to temperatures at diiierent locations for controllingthe heat supplied to a building orv the like, and has for its principal object the provision of an improved system and method of operation whereby heat is supplied relation between different temperatures such as the heating medium .and outside temperatures. In eiiectuating such control, use has been made of a bridge network which (1) includes elements responsive tothe various control temperatures and (2) functions through a gaseous electricdischarge device or the like to`-contrl an electric motor or other instrumentality whereby the supply of heating medium is regulated.

Such heat control systems, however, have not operated with the highest degree of economy for the reason that they function to maintain. a substantially linear. relation between the control temperature and the temperature oi theheating medium. While such a relation may be desirable during daytime operation. when the building is occupied. it is frequently unessential at night when the main consideration is protection of the I contents o f the building rather than the comfort of its occupants.

In accordance with the present invention, 1m`- proved economy in fuel consumption is achieved by the provision of means whereby the heating medium is controlled in accordance with the outside temperature during the day and. during the night, is maintained at a relativelylow level while the outside temperature is abovea predetermined criticalv value, but is maintained at a lhigh'er leveiat outside temperatures below this critical value.

IThe invention will be better understood from the -following description considered in connec' tion with the accompanying drawing. and its Ascope is indicated by the appended claims.V

Referring to the drawing,

Figure 1 is a wiring diagram of the improved heat control system, and

Figure 2 are explanatory curves'relating to th operation of the system of Fig. 1.

This system includes a switch I0, which is operated by a coil Il for controlling 'an electric motor or other instrumentality (not shown) for regulating the supply ot heat.

Current is supplied to the switch operating coil Il from a suitable source through'supply terminais I2 Il, a transformer' I4, andan electron discharge device I5 which trol grid I6 and may be of the gaseous type.

The cathode e1ectrode of the device i5 is com nected to the control grid I8 through a source of bias potential l1., the terminals ISE- of. a bridge network I8', and a resistor 2|. To the other ter` minals 22-23. of the ,networki is connected an alternating current source illustrated as a transformer 24. -v

4The network I8 includes in its different arms (1) a zero temperature coemcient resistor 25, (2) a zero temperature coeiiicientsresistor 26,4 (3) `a zero temperature coeiiicient resistor '2l and a high temperature oeilicient resistor 28 which is re.-

sponsive to the temperature of the heat supply medium, and (4) either a high temperature coresistor 29 is preferably mounted in a location eiiicient resistor 29 or a zero temperature coeicient resistor 30. depending on the position of a day-night three-blade switch 3i which is operable to "day and"night closed positions. The

where it responds 'to outside temperature.

Also'so mounted as to be responsive to outside temperature is a thermostat 32 or other temperature-responsive element which is connected in' circuitfwith an alternating current source 33, the

operating coil 34* of `a switch 35, and the middle .blade 3l of the day-night switch 3|, the element 32 being so adjusted as to close the circuit when the outside 'temperature decreases to a predetermined critical value. 1

Assuming the switch 3| to be closedin its day position, the resistor 29 is connected through the blade 36 intothe network I8, and the network resistor 21 is short-circuited through the blade 33. With these connections, there is aplplied to the control grid I6 a potential whichy varieswith change inthe outside temperature and which functions to change the heating medium temperature, and consequently the temperature of the resistor 28, until balance ofI the bridge network is restored.

II'he operation of the system under these conditions'is illustrated by the curve a of Fig. 2, Y

which shows a linear relation between outside temperature and the temperature oi the heating medium. Heretofore, Ia similar,linear relation, illustrated by the curve 11, has been maintained duringnight operation, suitable adjustment, of course, being made so that less heat isvsupplied during the night than during the day. Operation v ci' thepresent system in the night position ofithe switch, howeverpis along' a curve of the. type illustrated by the curve uc" oi Fig. 2, re-v is provided with a concross-hatched area of this ilgure.

sulting in a fuel saving commensurate Avviththe Thus, with the switch 3| closed in its I8 of the resistor 30 which is of a value corresponding to that of the resistor 29 at some predetermined temperature such as 65, andF the blade such as 35, f or example, the contacts of the de-` vice 32 are closed, vthe operating. coil 34 is energized and the switch 35 is closed, thus sh0rtcircuiting a part of the resistor .21 and causing the heating medium temperature to be maintained at the higher level indicated by the curve c.

Itis apparent, of course, that temperature values other than those illustrated may be utilized to control the night operation of the system, and that a substantial fuel savingcommensurate with the cross-hatched area of Fig. 2 is effected.

I claim as my invention:

1. `In a heat control systemof the type wherein the balance of a bridge network is dependent on the potential drops of high temperature coecient elements connected respectively in different arms of said bridge network and maintained respectively at outside and heating me-` Ll, i

xnightn position, the blade 36 connects 'into the network medium temperature responsiveelement, meansA for alternatively connecting said outside temperature responsive element or the other of said zero temperature coeiilcient elements in said net- Work, and means for short-circuiting a predetermined portion of said series-connected zero temperature coefficient element in response to a predetermined critical value of said outside temperatu\ 2. In a heat control system of the type wherein the balance of a bridge network is dependent on the potential drops of high temperature coeilicient elements connected respectively in different arms of-said bridge network and maintained respectively at outside and heating medium temperatures, the combination of a pair of zero temperature coeiiicient elements one of which is connected in series with said heating mediuin temperature responsive element, a switch for alternatively connecting said outside temperature responsive element or the other Yoi said zero temperature coefficient elements in said network, and means controlled by said switch and responsive to outside temperature for shortcircuiting a predetermined portion of said series connected zero temperature coefficient element.

PERRY C. SMITH. 

